Bacillus Thuringiensis
Bacillus thuringiensis ("Bt") is a gram-positive soil bacterium, which produces endogenous crystalline inclusions upon sporulation. Early in this century, these bacteria were found to be insecticidal (Berliner, 1915). Some years later, their insecticidal activity was found to reside in the proteins present in their crystals, hereinafter referred to as "insecticidal crystal proteins" or "ICPs". Since then, the Bt strains, spores, crystals and ICPs have been used as biological insecticides in commercial formulations.
The limited spectrum of these insecticidal proteins allows any naturally occurring predators of the target insects to survive. The continued presence of these predators prevents further outbreaks of the insects. Furthermore, these Bt proteins have the advantage that they are rapidly degradable and that no stable residues accumulate in the environment.